This invention relates to a diagnostic system for effectively testing the operation of sensors in a refrigeration system and for providing a warning when at least one of the sensors is found to be defective.
In refrigeration systems, and particularly in large commercial and industrial air conditioning systems, several of the operating variables or parameters are monitored for control and safety reasons. For example, the pressure of the refrigerant in the condenser and in the evaporator, the temperature of the refrigerant at the compressor discharge, the oil temperature, and the motor current may all be sensed by separate sensors. The sensor outputs may be used to control the operation of the air conditioning system and also to detect when dangerous faults exist, such as when the condenser refrigerant pressure reaches a preset maximum allowable level.
Unfortunately, in the past there was no way to check the individual sensors to confirm that they were functioning properly. The failure of a sensor could go undetected or cause undesirable system operation without generating a system fault. If a sensor malfunctions there is no way of discovering this in the prior refrigeration systems.
This shortcoming has now been overcome by the present invention. By means of a relatively inexpensive arrangement, faulty sensors are automatically detected and a fault warning message is displayed when a defective sensor is present.